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Solution: Count and Say

Explore the count and say coding problem by learning to track consecutive digits efficiently. This lesson teaches you to generate sequence strings using the knowing what to track pattern, improving your problem-solving skills for coding interviews.

Statement

The “count and say” is a sequence of strings built by describing the previous string:

  • The sequence starts with countAndSay(1) = “1”

  • For n > 1, countAndSay(n) is created by run-length encoding the string countAndSay(n - 1).

Run-length encoding (RLE) works by grouping identical consecutive characters and replacing each group with the count of characters followed by the character itself. For example, the string “15224” is read as: one 1, one 5, two 2s, and one 4, producing “11152214”.

Given a positive integer n, return the nthn^{th} string in the count-and-say sequence.

Constraints:

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